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THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



by the supporters of spontaneous generation was 

 at first sight much less attractive. They said 

 that the modifying effect of superheating had 

 nothing to do with the destruction of germs, 

 which were dead long before the boiling-point 

 was reached, and that it ought to be ascribed to 

 disintegrating changes, set up by the high tem- 

 perature, of such a character as to indispose the 

 fluid for vital transformation. If Bastian's death- 

 point experiments should be finally established, 

 this last view must be accepted as the only doc- 

 trine which is compatible with them ; but the 

 germ - theorists, though they have not yet at- 

 tempted to displace the results of that investiga- 

 tion (as for the sake of settling a knotty scien- 

 tific question it is to be hoped they will soon 

 muster courage to do), have held firmly to their 

 old notion, and Pasteur especially has reiterated 

 of late the formula which he propounded in 

 1S62, that germs are killed in acid fluids at 100° 

 C, while neutral or faintly alkaline fluids exercise 

 a protective influence during the heating which 

 enables any germs within them to endure a tem- 

 perature of a few degrees more. Even in these 

 fluids he maintained, and still maintains, that all 

 germs are certainly deprived of life or of fecun- 

 dity — the only practicable test of life — by a tem- 

 perature of 110°. An example of an undoubted 

 fact pointing in this direction is afforded by the 

 behavior of urine, which is, in its normal state, 

 an acid fluid. If boiled in its natural condition 

 for a very few minutes and then protected, it sel- 

 dom (until quite recently it was thought never) 

 evolves bacterial life. If it has first been ren- 

 dered neutral, or about neutral, by the addition 

 of an alkali before boiling, it is now known often 

 to prove fertile. Pasteur's theory would ascribe 

 this to his assumed fact that germs can bear 

 a higher temperature in neutral than in acid 

 fluids. 



All that was needed in this case to test the 

 truth of Pasteur's doctrine about the protective 

 power of neutral fluids was to boil the urine in 

 its acid state, which, according to Pasteur him- 

 self, would kill all previously-existing germs, and 

 then add the alkali afterward, and see if it would 

 not be equally efficacious in promoting the evolu- 

 tion of life. If it proved so, there would be an 

 end of Pasteur's plausible theory on the point. 

 Accordingly, Bastian devised a very pretty ar- 

 rangement for testing the question. He placed 

 in one of his retorts a measured quantity of urine 

 of ascertained acidity ; he then prepared a small 

 tube, into which he poured a quantity of liquor 

 potassae, somewhat less than enough to neutralize 



the urine. The proportion which he found to give 

 the best results was about three-fourths of the 

 neutralizing dose. Having done this, he sealed 

 the small tube in the blowpipe, drawing out the 

 end sufficiently to cause it to break readily with 

 a smart tap. The potash - tube thus prepared 

 was heated for a long time, varying from fifteen 

 minutes to two hours, in water which was kept 

 boiling with the object of destroying any life, if 

 life there could be, in the liquor potassse and the 

 air within the tube. After this the tube was 

 dropped with its thinned end downward, gently 

 into the retort, which was then boiled and her- 

 metically sealed in the usual way. After cooling, 

 the retort was briskly shaken, so as to break the 

 point of the small tube and allow the contained 

 fluid to mix with and neutralize the urine. A 

 number of retorts thus prepared were placed in 

 a bath kept at a high incubating temperature, 

 about 122°, together with one (or sometimes 

 more) in which the potash - tube was left un- 

 broken, as a control-experiment. After a day or 

 two, or even less, the contents of the retorts 

 which had been neutralized almost invariably 

 putrefied just as it was known they would have 

 done if the alkali had been added before the 

 boiling, while the still acid urine in the control- 

 flask remained permanently barren. It followed 

 that the vivifying influence of the alkali was due 

 to some chemical or other molecular action, and 

 not to its supposed power of warding off heat, 

 and the experiment, coupled with the universally- 

 accepted fact that all germs perish in urine boiled 

 in its natural state, left apparently no alternative 

 but to accept the conclusion that life had ap- 

 peared de novo in the neutralized fluid. We may 

 mention that the reduction above mentioned in 

 the quantity of the liquor potassae below the 

 neutralizing proportion was at first adopted em- 

 pirically, and it was supposed to be needed only 

 to compensate for the loss of part of the con- 

 tents of the retorts during the process of boil- 

 ing. Another and probably more potent reason 

 is, that the urine may undergo changes which re- 

 duce its acidity not only while exposed to boiling 

 heat, but at a slower rate during the whole time 

 that it remains in the more moderate temperature 

 of the incubating bath. There seems, however, 

 no present reason to doubt that exact neutraliza- 

 tion is the state in which putrefaction most read- 

 ily occurs, and, to insure that, it is safer to keep 

 the supply of liquor potassse below than above 

 the mark, because in the former case the acidity 

 would gradually come down to the neutral point, 

 while anything like an excess of alkali has been 



